Convention priority for this application is claimed to Korean Patent Application No. 2000-12911 filed Mar. 14, 2000; Korean Patent Application No. 2000-28471 filed May 25, 2000; Korean Patent Application No. 2000-31492 filed Jun. 8, 2000; and Korean Patent Application No. 2000-67244 filed Nov. 13, 2000.
The present invention relates to physiologically active materials separated from cereals and a process for preparation thereof More particularly, the present invention relates to ferulic acid and arabinoxylan, both being of physiological activity, separated from cereal bran and a process for separation thereof, which is a combined process of extrusion and the subsequent treatment with cell wall hydrolyzing enzymes for cereal bran.
Cereal bran is a byproduct generated in the polishing process. The cereal bran contains a pericarp, a seed coat, an aleurone and the like, exclusive of the hull from the outer layer of cereals and occasionally contains a part of germ and endosperm as a result of the polishing process (Kulp, K. et al., Handbook of Cereal Science and Technology, Marcel Dekker, Inc., Switzerland, 2000).
The cell wall of cereal bran consists of macromolecules such as cellulose, hemicelluloses, lignin, glycoprotein, and the like. These molecules do not exist in free form, but mostly bind strongly to each other via covalent bonds, hydrogen bonds and ionic bonds, existing in insoluble form (Dey, P. M. and Brinson, K. Adv. Carbohydr. Chem. Biochem., 42: 265-382, 1986).
Aside from the above macromolecules, cereal bran contains vitamin and mineral, etc. in the cell wall. Particularly, having been lately characterized as functional active materials, phenolic compounds such as caffeic acid, sinapic acid, ferulic acid and coumaric acid are disclosed (Clifford, M. N. et al., J. Sci. Food. Agric., 79:373-378, 1999).
One of the most abundant phenolic compounds in cereal bran is the ferulic acid represented by the following formula I. It has been known until now that the ferulic acid has several physiological activities such as antioxidant, anticancer, anticholesterol, antibiotic, anti-mutation and anti-inflammatory, etc. (Castelluccio, C. et al., Biochem. J., 316:691-694, 1996; Fernandez, M. A. et al., J. Pharm. Phamacol., 50:1183-1186, 1998; Saija, A. et al., Int. J. Pharmacol., 199:39-47, 2000). 
Ferulic acid does not exist in free form in the cell wall of the cereal bran, but forms an insoluble linkage that is bound to arabinoxylan, one of cell wall components, by ester linkage (Saulnier, L. and Thibault, J. F., J. Sci. Food Agric., 79: 396-402, 1999).
Ferulic acid, though present in cereal bran, has almost no physiological activity, because there are no enzyme systems which can break the ester linkage of ferulic acid and arabinoxylan in the human body. Therefore, very limited bioavailability can be obtained even if cereals are ingested (Saunders, R. M. et al., Cereal Chem., 49:436-442, 1972; Annison, G. et al., World""s Poult. Sci. J., 47:232-242, 1991). Arabinoxylan, one of the hemicelluloses constituting the cell wall of cereal bran, is a sort of complex carbohydrate. It has recently been found that arabinoxylan has several physiological activities, such as immunomodulating effect, anti-diabetes, increasing resistance to infection, therapeutic aid versus malignant tumors, water-soluble dietary fiber and the like, and thus has attracted particular attention as a new functional food material (Ghoneum, M., Int. J. Immunother., 104(2): 89-99, 1998; Miyazaki, H. et al., Int. J. Immunophamacol., 16(2): 163-170, 1994; Menon, P. V. et al., J. Nutr., 106(4): 555-562, 1976).
Like ferulic acid, arabinoxylan does not exist in free form in the cell wall of cereal bran, but is present as an insoluble form bound with other cell wall components (Hatfield, R. D. et al., J. Sci. Food Agric., 79: 404-407, 1999). The absence of enzyme systems which can dissolve such insoluble materials in the human body makes the bioavailability of arabinoxylan very low.
Generally, food processing is carried out by steaming, roasting, drying, grinding and the like. Because these cause only physical changes of food, it is very difficult to separate the ferulic acid and arabinoxylan, which exist as insoluble materials in cereal bran, from the other cell wall components.
In addition, the rigid structure of cereal cell walls rarely allows enzymes to infiltrate thereinto owing to its being highly dense, which makes it very difficult to separate insoluble materials in cereal bran by individual enzyme treatment processes.
Because the extrusion process accompanies not only high temperature and pressure, but also a strong shearing force, a rigid structure of plant cell walls is efficiently disintegrated by the extrusion process (Hwang et al., J. Korean Soc. Food Nutr., 23(2):358-370, 1994).
Therefore if cereal bran is treated with individual enzymes, it is difficult for the enzymes to infiltrate into the cell wall structure. But if enzyme treatment follows an extrusion process, it is possible to separate physiologically active materials, since enzymes can readily infiltrate into the cell wall structure, which is already disintegrated by extrusion.
Bearing the above-mentioned backgrounds in mind, the present inventors have accomplished the separation of ferulic acid and arabinoxylan by a combined process, first comprising extrusion in order to physically break down the rigid structure of cereal bran derived from cereals such as rice, wheat, rye, corn, barley, oats and the like, and secondly the subsequent treatment with cell wall hydrolyzing enzymes to hydrolyze insoluble linkages.
Accordingly, it is an object of the present invention to provide physiologically active materials such as ferulic acid and arabinoxylan, which are separated from cereals.
It is another object of the present invention to provide a method of separating physiologically active materials from the above-mentioned cereal.
To accomplish the objects of the present invention, first, cereal bran derived from cereals such as rice, wheat, rye, corn, barley, oats and the like is injected into a twin screw extruder for extrusion, followed by hydrolyzing polymers of the bran with cellulase or hemicellulase, such as arabinase, xylanase, mannase, glucanase and the like, to separate physiologically active materials such as ferulic acid and arabinoxylan.
For the preparation of physiologically active materials from cereal bran, first, cereal bran is physically break down by extrusion from a twin screw extruder. The extrudate is dispersed in water and its cell wall material is decomposed by treatment with hydrolyzing enzymes. Subsequently, the hydrolysate is extracted with ethyl acetate, followed by concentration in vacuo to give ferulic acid. Seperately, the hydrolysate is centrifiltered and the filtrate is added with an xcex1-amylase, such as TERMAMYL 120L (Novozymes A/S, Denmark), for hydrolyzing starch. After ultrafiltration, the residue is dried to dryness to give water-soluble polysaccharides, including arabinoxylan.